trusty (3) gmtime_r.3posix.gz

NAME

       gmtime, gmtime_r - convert a time value to a broken-down UTC time

SYNOPSIS

       #include <time.h>

       struct tm *gmtime(const time_t *timer);

       struct tm *gmtime_r(const time_t *restrict timer,
              struct tm *restrict result);

DESCRIPTION

       For  gmtime():    The  functionality described on this reference page is aligned with the ISO C standard.
       Any conflict between the requirements described here and the ISO C standard is unintentional. This volume
       of IEEE Std 1003.1-2001 defers to the ISO C standard.

       The  gmtime()  function  shall  convert  the  time  in seconds since the Epoch pointed to by timer into a
       broken-down time, expressed as Coordinated Universal Time (UTC).

       The relationship between a time in seconds since the Epoch used as an argument to  gmtime()  and  the  tm
       structure  (defined  in  the  <time.h> header) is that the result shall be as specified in the expression
       given  in  the  definition  of  seconds  since  the  Epoch  (see   the   Base   Definitions   volume   of
       IEEE Std 1003.1-2001, Section 4.14, Seconds Since the Epoch), where the names in the structure and in the
       expression correspond.

       The same relationship shall apply for gmtime_r().

       The gmtime() function need not be reentrant. A function that is not  required  to  be  reentrant  is  not
       required to be thread-safe.

       The  asctime(),  ctime(),  gmtime(),  and  localtime() functions shall return values in one of two static
       objects: a broken-down time structure and an array of type char. Execution of any of  the  functions  may
       overwrite the information returned in either of these objects by any of the other functions.

       The  gmtime_r()  function  shall  convert  the time in seconds since the Epoch pointed to by timer into a
       broken-down time expressed as Coordinated Universal Time (UTC). The broken-down time  is  stored  in  the
       structure  referred  to  by  result.  The  gmtime_r()  function shall also return the address of the same
       structure.

RETURN VALUE

       Upon successful completion, the gmtime() function shall return a pointer to a struct tm. If an  error  is
       detected, gmtime() shall return a null pointer    and set errno to indicate the error.

       Upon  successful  completion,  gmtime_r()  shall  return  the  address of the structure pointed to by the
       argument result.  If an error is detected, gmtime_r() shall return a null pointer.

ERRORS

       The gmtime() function shall fail if:

       EOVERFLOW
              The result cannot be represented.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       The gmtime_r() function is thread-safe and returns values in a user-supplied buffer instead  of  possibly
       using a static data area that may be overwritten by each call.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       asctime()  , clock() , ctime() , difftime() , localtime() , mktime() , strftime() , strptime() , time() ,
       utime() , the Base Definitions volume of IEEE Std 1003.1-2001, <time.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. In the event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .